When a jet-powered aircraft lands, the landing gear brakes and imposed aerodynamic drag loads (e.g., flaps, spoilers, etc.) of the aircraft may not, in certain situations, be sufficient to slow the aircraft down in the required amount of runway distance. Thus, jet engines on most aircraft include thrust reversers to enhance the braking of the aircraft. When deployed, a thrust reverser redirects the rearward thrust of the jet engine to a generally forward direction to decelerate the aircraft. Because the jet thrust is directed generally forward, the jet thrust also slows down the aircraft upon landing.
Various thrust reverser designs are commonly known, and the particular design utilized depends, at least in part, on the engine manufacturer, the engine configuration, and the propulsion technology being used. Thrust reverser designs used most prominently with turbofan jet engines fall into three general categories: (1) cascade-type thrust reversers; (2) target-type thrust reversers; and (3) pivot door thrust reversers. Each of these designs employs a different type of moveable thrust reverser component to change the direction of the jet thrust.
Cascade-type thrust reversers are normally used on high-bypass ratio jet engines. This type of thrust reverser is located on the circumference of the engine's midsection and, when deployed, exposes and redirects air flow through a plurality of cascade vanes. The moveable thrust reverser components in the cascade design includes several translating sleeves or cowls (“transcowls”) that are deployed to expose the cascade vanes. Target-type reversers, also referred to as clamshell reversers, are typically used with low-bypass ratio jet engines. Target-type thrust reversers use two doors as the moveable thrust reverser components to block the entire jet thrust coming from the rear of the engine. These doors are mounted on the aft portion of the engine and may form the rear part of the engine nacelle. Pivot door thrust reversers may utilize four doors on the engine nacelle as the moveable thrust reverser components. In the deployed position, these doors extend outwardly from the nacelle to redirect the jet thrust.
The primary use of thrust reversers is, as noted above, to enhance the braking of the aircraft, thereby shortening the stopping distance during landing. Hence, thrust reversers are usually deployed during the landing process to slow the aircraft. Thereafter, when the thrust reversers are no longer needed, they are returned to their original, or stowed, position.
The moveable thrust reverser components in each of the above-described designs are moved between the stowed and deployed positions by actuators. Power to drive the actuators may come from one or more drive motors, or from a hydraulic or pneumatic fluid system connected to the actuators, depending on the system design. A drive train may interconnect the actuators (and drive motors, if included) to maintain synchronous movement of the moveable thrust reverser components. The drive train may also include a disk brake assembly that applies a brake torque when the thrust reversers are stowed to prevent inadvertent deployment. Typically, the drive train is coupled to the actuators via a plurality of flexible rotating shafts.
In some configurations, the flexible shafts between each of the actuators and the drive train have different lengths. For example, in some configurations, a shorter flexible shaft may be coupled proximate the disk brake assembly and may receive disk brake rotational energy experienced during cowl deployment and impact with the deployment stops. Because of the shaft's short length, the resulting load received by the shaft may be relatively high. This increased load may increase the wear experienced by the flexible shaft. As a result, the flexible shaft may need to undergo more frequent maintenance or replacement.
Hence, there is a need for a flexible shaft that improves on one or more of the above-noted drawbacks. Namely, a flexible shaft that is configured to transfer torque effectively, decrease frequency of maintenance and/or replacement. The present invention addresses one or more of these needs.